Mass sensor

A mass sensor is provided for determining the mass of small objects. The mass sensor has a plurality of nanostructures attached to a substrate. The nanostructures and the substrate are irradiated with an electromagnetic wave to determine a first mechanical-electromagnetic resonant frequency of the mass sensor. After a particle is attached to the nanostructures, the substrate and the nanostructures to which the particle is attached are irradiated with an electromagnetic wave to determine a second mechanical-electromagnetic resonant frequency of the mass sensor. A mass of the particle is determined based on a difference between the first and second mechanical-electromagnetic resonant frequencies.